Generally, indicia readers (e.g., barcode scanners) fall into one of three categories: wand scanners, laser scanners, and imaging barcode readers.
Wand scanners generally include a light source and photodetector housed in a pen-shaped housing. A user drags the wand reader across a code symbol (e.g., a barcode), and a signal is generated that represents the bar-space pattern of the barcode.
Laser scanners typically include a laser diode and lens combination to generate a collimated light beam. The beam is swept back-and-forth across a barcode by a reciprocating mirror. The light reflected from the barcode is collected and sensed by a photodetector. The result is an electronic signal that corresponds to the bar-space pattern of the barcode.
Imaging indicia readers (i.e., barcode readers) include an image sensor (e.g., CCD) and a group of lenses (i.e., lens group) for focusing the image of a target (i.e., barcode) onto the image sensor. The image sensor captures a digital picture of the barcode, and a processor running algorithms detects and decodes the barcode from the image. The optical subsystems (i.e., modules) in an imaging barcode reader responsible for creating a good image of a barcode is known as the imaging engine.
Most thin-profile, hand-held, mobile computing devices (e.g., smart-phones) now have integrated cameras that can be used as the imaging engine for indicia reading, and numerous applications for barcode scanning have been developed for these devices. While these applications perform reasonably well for the casual user, they lack the features, functions, and performance present in dedicated imaging barcode readers. Illumination, alignment, and image quality may all suffer when using a mobile computing device's camera as the imaging engine for barcode scanning.
Because most users want to carry only one mobile computing device, they will be reluctant to trade their mobile device for a dedicated indicia reader. A need, therefore, exists for a dedicated imaging indicia reader that is integrated within a hand-held mobile computing device. This integration, however, puts severe limitations on the imaging indicia reader's design. Unique design approaches and construction methods must be combined to allow for such novel integration. One such approach incorporates an optical structure within the housing of the indicia reading module.